oceans final- chapter 14

What do we know about trophic structure in coral reef communities? What do we know about competition and predation in these communities?

- coral reef communities have high primary production because they are in nutrient poor waters which is why they recycle nutrients amongst other corals and organisms -corals compete for space by growing upward and out (blocking neighbors light) or by directly attacking them. - Coral predation is similar to grazing by herbivores. When a piece of coral is bitten off it just grows back (like plants). Coral predation effects numbers and types of corals that live on a reef

What are the abiotic requirements for coral reefs to form? Do you think these condition have anything to do with the decline of coral reefs?

-shallow warm (and clear) waters allow coral reefs to form. -coral reefs are declining which may be due to the increasing sea level and melting of cold, polar ice formations. pollutants could be a cause of cloudy water

How do coral reefs grow?

-zoonanthellae help corals make their calcium carbonate skeletons at a fast enough pace to produce coral reefs. -grow in shallow warm waters (shallow because they need light) -only found on continental shelves around islands or on top of seamounts -do not do well near river mouths where there is not a lot of salt and a lot of silt (making water cloudy)

What are the three different types of coral reefs and where do they form?

1) fringing reefs- form near shore in tropical waters (will often encircle an island) (coral begins as a fringing reef) 2) barriers reefs- form along shore or farther from shore (due to a lagoon separating it from shore) 3) Attols- circular reef structure formed around a central lagoon (formed when a volcanic island is formed)

What is a trophic cascade?

A trophic cascade is when changes in the abundance of an organism (fish) result in changes at other trophic levels of the food chain (coral).

What is coral bleaching and how does it occur?

Coral bleaching is the first sign of stress where the coral expels its zoonxanthellae; this causes coral to look white

What evidence is there that reef sharks are part of a trophic cascade in coral reef communities?

When shark depletion occurred, the number of predator fish that they eat (groupers) rose and they in turn ate more smaller grazing fishes than are normally eaten (because there are more groupers now that there are less sharks)

What gives coral its color?

Zooxanthellae live in produce the color pigments in coral -visible through the clear body of polyp

What is a major component of the coral reefs?

calcium carbonate forms base of coral reefs

What type of organism is coral?

coral is a general term for several different groups of cniderians

What is the difference between hard and soft coral?

hard coral= reef builders who provide a calcareous skeleton and nearly all have zooxanthellae. soft coral= don't build reefs (because coral larvae need to settle on a hard surface) but most have zooxanthellae and produce calcareous skeleton.